JP6550930B2 - Active sonar device and signal processing method thereof - Google Patents

Description

  The present invention relates to an active sonar device and a signal processing method thereof, and more particularly to an active sonar device for removing artificial noise and a signal processing method thereof.

  The active sonar device is used to detect and display a target by transmitting a sound wave from a transmitter into water and receiving a reflected sound from the target with a receiver. Active sonar devices, for example, in sea areas where there are many artifacts, such as harbors, receive not only reflected sound from the target but also reverberation from the sea floor and sea surface, natural noise due to waves and heat, and artificial noise from ship propulsion devices. There are many waves. Therefore, in the active sonar device, it is necessary to reduce the influence of the received signal other than the reflected sound from the target, in particular, the artificial noise due to the propeller of the ship and the like.

  As a technique for removing the influence of artificial noise such as a ship, there is a technique disclosed in Patent Document 1, for example. The active sonar device described in Patent Document 1 divides a received wave signal obtained when transmitting a sound wave into unit reflected wave data, and stores in advance acoustic data before transmitted sound wave including artificial noise stored in advance. Among them, the portion with the highest correlation for each unit reflected wave data is used as data for noise removal.

  Moreover, the acoustic noise monitoring system of the ship of patent document 2 provides a sound pressure sensor in noise generating apparatuses, such as an engine and a propeller, and makes the signal of the sound pressure sensor of the vicinity of a sonar the background noise in a sonar. The correlation with the signal obtained from the sound pressure sensor installed in each device is analyzed to identify the noise generating device having a large contribution to the background noise of the sonar.

  Further, the active sonar device described in Patent Document 3 is obtained when transmitting no sound wave for a plurality of unit reflected waves obtained by dividing and obtaining a reflected wave obtained by transmitting a sound wave into water from a wave transmitting / receiving unit on a time axis. A portion of the noise wave having the highest correlation in the waveform is extracted as noise wave data for removal. A noise removal unit reflection wave is sequentially generated by subtracting the noise wave data for removal corresponding to each unit reflection wave in an amplitude manner to sequentially generate a noise removal unit reflection wave, and this noise removal unit reflection wave is converted to a continuous reception reflection wave signal The signal is converted and output to the received signal processing unit.

Japanese Patent No. 3452019 JP 2004-212331 A Japanese Patent Laid-Open No. 2001-272459

  However, in the active sonar devices and acoustic noise monitoring systems described in Patent Documents 1 to 3, means for determining that artificial noise is included in acoustic data before acoustic wave transmission and reflected wave data after acoustic wave transmission, The noise removal means when the artificial noise changes in the azimuth direction has not been considered. In particular, when artificial noise moves in the azimuth direction, there is no artificial noise in acoustic data before transmission of sound waves, and noise removal is performed in the case where there is an azimuth in which artificial noise exists in acoustic data including reflected waves. Necessary. Further, when there is a ship moving in the azimuth direction at high speed in front of the active sonar device, the noise caused by such a ship is Doppler shifted before and after the sound wave transmission. It has not been considered to determine and remove such noise.

  An object of the present invention is to provide an active sonar device capable of determining various artificial noises in acoustic data before and after sound transmission, and a signal processing method thereof.

  The active sonar device according to the present invention comprises a wave transmitter for transmitting a sound wave, a wave receiver for receiving a sound wave and outputting sound data, and sound data of one or more directions in which artificial noise is present before sound wave transmission. It has an artificial noise extraction unit that generates replica noise data of a predetermined time length, and an artificial noise removal unit that removes artificial noise from acoustic data after sound wave transmission using the replica noise data.

  The signal processing method of the active sonar device according to the present invention is a signal processing method of an active sonar device having a wave transmitting unit for transmitting a sound wave and a wave receiving unit for receiving a sound wave and outputting acoustic data. Replica noise data having a predetermined time length is generated from acoustic data in one or more directions in which artificial noise previously exists, and the artificial noise is removed from the acoustic data after sound wave transmission using the replica noise data .

  ADVANTAGE OF THE INVENTION According to this invention, the various artificial noises in the acoustic data before sound wave transmission and after sound wave transmission can be determined in an active sonar apparatus.

FIG. 1 is a block diagram showing the configuration of the first embodiment. FIG. 2 is a diagram showing acoustic data received by the transducer unit 1 of FIG. FIG. 3 is a diagram showing acoustic data of the direction θ1 of FIG. FIG. 4 is a diagram showing acoustic data of the direction θ2 of FIG. FIG. 5 is an explanatory diagram illustrating the timing of acquiring the artificial noise replica according to the first embodiment. FIG. 6 is a block diagram showing the configuration of the artificial noise extraction unit of FIG. FIG. 7 is a diagram showing a cell obtained by dividing the acoustic data of FIG. 2 by time and azimuth axes. FIG. 8 is a block diagram showing the configuration of the artificial noise removal unit of FIG. FIG. 9 is an explanatory diagram illustrating the timing of acquiring the artificial noise replica according to the second embodiment. FIG. 10 is a block diagram illustrating a configuration of the second embodiment. FIG. 11 is a block diagram showing the configuration of the artificial noise extraction unit of FIG.

  FIG. 1 is a block diagram showing the configuration of the active sonar apparatus according to the first embodiment of the present invention.

  As shown in FIG. 1, the active sonar device of the present embodiment includes a transducer unit 1 for transmitting and receiving sound waves, a switch 2 for separating received acoustic data before and after transmission of sound waves, and transmission A pre-transmission sound storage unit 3 for storing pre-acoustic data and an artificial noise extraction unit 4 for extracting artificial noise from the stored pre-transmission sound data are provided. Further, in the active sonar device of the present embodiment, a reflected wave storage unit 5 for storing acoustic data including a reflected wave after sound wave transmission, and an artificial noise removing unit 6 for removing artificial noise extracted from the acoustic data after sound wave transmission. And a received signal processing unit 7 that processes the acoustic data after the removal of the artificial noise, and a display operation unit 8 that displays the processing result.

  FIG. 2 is a diagram showing acoustic data received by the transducer unit 1 of FIG. The horizontal axis in FIG. 2 is time, and newer acoustic data is shown at the top of the figure. The horizontal axis is the azimuth, and two-dimensionally illustrates the strength of the acoustic data. The whiter the sound level, the higher the sound level.

  FIG. 3 is a diagram showing acoustic data in the azimuth θ1 of the artificial noise before the sound wave transmission. FIG. 4 is a diagram showing acoustic data in the azimuth θ2 where the level of the artificial noise becomes high during the time when the natural noise is dominant. As described above, the acoustic data may be a collection of acoustic data as shown in FIGS. 3 and 4 in each direction.

  As shown in FIG. 2, after transmitting the sound wave, the sound level is high due to reverberation that the sound wave emitted from all directions and for a while is reflected from the surrounding structures and the seabed, and then the sound level gradually decreases, and natural noise such as waves Becomes the dominant time.

  For example, artificial noise caused by a ship appears as a white vertical line as shown in FIG. In the upper part of the figure, the high azimuth of artificial noise at times when natural noise dominates, for example, azimuth θ2, is offset from the high azimuth θ1 of artificial noise before transmission of sound waves, and acoustic data is not high before transmission of sound waves. It has become a direction. From this, it can be seen that the artificial noise source is moving.

  According to the present invention, in the situation shown in FIG. 2, the acoustic data when the acoustic level is high at θ2, for example, can be determined to be the artificial noise received in the azimuth θ1 before the sound wave transmission. Further, the same acoustic data as the artificial noise can be deleted from the acoustic data after the sound wave transmission.

  FIG. 5 is an explanatory diagram showing the timing for acquiring the artificial noise replica of the first embodiment. As shown in FIG. 5, the active sonar device of the present embodiment periodically transmits an acoustic wave at times t1, t2, t3 and t4 at, for example, a cycle T. A replica of artificial noise is acquired from acoustic data for a predetermined time δt before the time t1 to t4 at which sound waves are transmitted. Based on the acquired replica, the artificial noise of the acoustic data after the transmission until the next sound wave is transmitted is removed. That is, the artificial noise between t1 and t2 is removed based on the artificial noise replica acquired from the acoustic data before t1.

  Referring back to FIG. 1, each component of the active sonar device will be described. The transducer unit 1 transmits sound waves in all directions. Also, it receives sound waves from all directions and outputs acoustic data to the switch 2.

  The switch 2 switches the output destination of the acoustic data from the transducer unit 1. Specifically, the switch 2 sets the output destination of the acoustic data of the sound wave received at a predetermined time before the sound wave transmission to the sound memory unit 3 before transmission. The switch 2 switches the output destination of the acoustic data after the sound wave transmission to the reflected wave storage unit 5.

  The artificial noise extraction unit 4 extracts artificial noise from the pre-transmission acoustic data stored in the pre-transmission acoustic storage unit 3. The artificial noise extraction unit 4 outputs the extracted artificial noise to the artificial noise removal unit 6.

  FIG. 6 is a block diagram showing the configuration of the artificial noise extraction unit 4. As shown in FIG. 6, the artificial noise extraction unit 4 includes an artificial noise presence determination circuit 41, an artificial noise removal data generation circuit 42, and an artificial noise Doppler shift generation circuit 43.

  The artificial noise presence / absence determination circuit 41 determines the direction in which the artificial noise is present from the acoustic data before the sound wave transmission. For example, in the artificial noise presence / absence determination circuit 41, the sound level and the threshold value of the sound length are set in advance. When the pre-transmission acoustic data is input, the artificial noise presence / absence determination circuit 41 performs peak picking in the azimuth direction, and detects an azimuth in which the acoustic level and acoustic length exceed the threshold in the pre-transmission acoustic data. The detected orientation is stored as an orientation in which artificial noise is present. Here, if there are one or more azimuths whose acoustic level or acoustic length exceeds the threshold, all azimuths are stored as the azimuths in which artificial noise is present.

  After the artificial noise removal determination circuit 41 determines the direction in which the artificial noise exists in the artificial noise removal data generation circuit 42, the artificial noise is present before the sound wave transmission for each direction in which the acoustic level or acoustic length exceeds the threshold. Replica noise data having a predetermined length of time is generated from the acoustic data of one or more orientations.

  Further, the artificial noise Doppler shift generation circuit 43 assumes a plurality of different Doppler shift frequencies for one or more azimuths where the artificial noise existed before the sound wave transmission, and generates replica noise data of the assumed plurality of frequencies. For example, the artificial noise Doppler shift generation circuit 43 may be set in advance with parameters for generating a Doppler shift frequency such as a Doppler shift frequency step Δf, an upper limit fmax, and a lower limit fmin. Then, with respect to replica noise data of the fundamental frequency f, replica noise data of a plurality of frequencies may be generated by changing the fundamental frequency by Δf from the fundamental frequency from f + Δf to fmax and from the fundamental frequency from f−Δf to fmin. Here, the signal processing unit 7 causes the display / operation unit 8 to display an input screen that prompts the user to input parameters for generating the Doppler shift frequency, and generates the Doppler shift frequency based on the operator's input. The artificial noise Doppler shift generating circuit 43 may be configured to set parameters for The artificial noise Doppler shift generation circuit 43 outputs a plurality of replica noise data different in Doppler shift frequency to the artificial noise removing unit 6.

  The artificial noise removing unit 6 removes artificial noise from acoustic data after sound wave transmission using replica noise data output from the artificial noise extracting unit 4. FIG. 7 is a block diagram showing the configuration of the artificial noise removing unit 6. As shown in FIG. 7, the artificial noise removal unit 6 includes a removal target data extraction circuit 61, an artificial noise removal data selection circuit 62, a removal data level adjustment circuit 63, and an artificial noise subtraction processing circuit 64. ing.

  The removal target data extraction circuit 61 divides the acoustic data after sound wave transmission including the artificial noise stored in the reflected wave storage unit 5 into acoustic data of a predetermined unit time for each predetermined azimuth. To do. The removal target data extraction circuit 61 thereafter determines the direction and time in which artificial noise is included, based on the sound level and sound length of the sound data of the unit time. The removal target data extraction circuit 61 extracts only acoustic data of a unit time including artificial noise exceeding a threshold set in each direction and each time segment.

  FIG. 8 is a diagram showing the azimuth and time cells determined by the removal target data extraction circuit 61 as containing artificial noise as black cells. The removal target data extraction circuit 61 performs, for example, an artificial noise removal process only on the acoustic data of the unit time of the azimuth and time determined to contain an artificial noise.

  The artificial noise removal data selection circuit 62 generates replica noise and Doppler output from the artificial noise extraction unit 4 for each of the acoustic data of unit time including the artificial noise extracted by the removal target data extraction circuit 61. Correlate with all shifted replica noise data. The artificial noise removal data selection circuit 62 selects the replica noise having the highest correlation as the artificial noise removal data.

The removal data level adjustment circuit 63 adjusts the sound level of the artificial noise removal data so that the remaining artificial noise is minimized when subtracting the artificial noise removal data from the unit time acoustic data including the artificial noise. To do. For adjustment, for example, an application algorithm disclosed in Japanese Patent No. 3452019 may be used. That is, artificial noise removal data A _n = W _an × X _a whose amplitude is controlled by the weighting coefficient Wa is generated from the artificial noise removal data Xa, and the artificial noise removal whose amplitude is controlled from the acoustic data S of unit time. by subtracting the use data a _n to generate a temporary removal processing data E _n. Then, the temporary removal processing data _{E n} is optimally determined whether right or wrong is denoised, the weighting factor _{W an, + 1} if not _{W an + 1 = W an +} μ × C n (C n: coefficient correction amount, mu: constant) Repeat the calculation and feedback step. Thus, temporary removal processing data _{E n} converges, square value of difference _{E n-1} which Motoma' the temporary removal processing data _{E n} and the previous ^{_{(E n -E n-1)}} 2 is set in advance If the constant value D is smaller than the constant value D, the adjustment is terminated. The removal data level adjustment circuit 63 outputs the adjusted sound level to the artificial noise subtraction processing circuit 64.

  The artificial noise subtraction processing circuit 64 generates artificial noise removal data whose sound level is adjusted based on the sound level output from the removal data level adjustment circuit 63 from the unit time reflected wave output from the removal target data extraction circuit 61. Subtract and output. In this way, it is possible to optimally remove artificial noise.

  The artificial noise removal data selection circuit 62, the removal data level adjustment circuit 63, and the artificial noise subtraction processing circuit 64 perform parallel processing on acoustic data of a plurality of unit times extracted by the removal target data extraction circuit 61. A plurality may be provided for the purpose.

  The acoustic data from which artificial noise has been optimally removed by the artificial noise subtraction processing circuit 64 is subjected to signal processing in the reception signal processing unit 7 in the subsequent stage, and the signal processing result is finally displayed on the display operation unit 8. For example, the signal processing unit 7 calculates the azimuth and distance of the object that reflects the sound wave transmitted from the transducer unit 1 based on the acoustic data from which the artificial noise is removed. The display operation unit 8 synthesizes the position of the object that reflects the sound wave transmitted from the transducer unit 1 with the surrounding map and displays it two-dimensionally.

  Further, the signal processing unit 7 may perform signal processing based on the acoustic data before the artificial noise is removed and display the processed signal on the display operation unit 8. For example, the signal processing unit 7 may display an image or a two-dimensional image of acoustic data as shown in FIG. 2 based on acoustic data before artificial noise is removed or acoustic data from which artificial noise has been removed. 3 and 4, signal processing for displaying an image of acoustic data in a specific direction as shown in FIGS. Then, an image showing the acoustic data two-dimensionally or an image of the acoustic data in a specific direction may be displayed on the display operation unit 8.

  Further, as shown in FIG. 7, the signal processing unit 7 is a signal for causing the display operation unit 8 to display a cell of the direction and time determined to contain artificial noise by the removal target data extraction circuit 61. Processing may be performed so that the display and operation unit 8 may display a cell having an azimuth and time determined to contain artificial noise. The displayed image is not limited to the image shown in FIG. 8 and may be any image that indicates the direction and time determined to contain artificial noise.

  As described above, the active sonar device of the present embodiment can determine that artificial noise is included in acoustic data before sound wave transmission and reflected wave data after sound wave transmission. Thereby, it is not necessary to calculate the azimuth and time data not including the artificial noise, and the calculation resource is saved.

  In addition, when the azimuth that includes artificial noise in the acoustic data before sound wave transmission differs from the azimuth that includes artificial noise in the sound data after sound wave transmission, artificial noise replica generation and artificial noise removal are performed. Is possible. Furthermore, it is also possible to cope with cases where there are a plurality of artificial noises and cases where there is Doppler shift. As a result, the accuracy of removing artificial noise is improved.

  Next, a second embodiment in which the timing for acquiring the artificial noise replica is changed will be described. FIG. 9 is an explanatory diagram showing the timing for acquiring the artificial noise replica of the second embodiment.

  In this embodiment, a replica of artificial noise is acquired from acoustic data of a time at which natural noise predominates next before transmitting a sound wave, and artificial noise of acoustic data of a time at which reverberation predominates before that time. It is embodiment which removes. That is, as shown in FIG. 9, when transmitting an acoustic wave at times t1, t2, t3 and t4, as shown in FIG. 9, from the acoustic data of the predetermined time .delta.t before the times t2, t3 and t4 at which the acoustic wave is transmitted next. Get a replica of the artificial noise. Based on the acquired replica, the artificial noise of the acoustic data of t1 to t2, t2 to t3, and t3 to t4 before the acoustic data of which the replica is acquired is removed.

  Moreover, the present embodiment is different from the configuration of the first embodiment in that all received acoustic data is stored in the reflected wave storage unit 5 and the switching unit 2 and the pre-transmission acoustic storage unit 3 are not provided. FIG. 10 is a block diagram showing the configuration of the second embodiment.

  The transducer unit 1 transmits sound waves in all directions, as in the first embodiment. On the other hand, the transducer unit 1 receives sound waves from all directions in the present embodiment and outputs the received acoustic data to the reflected wave storage unit 5.

  In the present embodiment, the artificial noise extraction unit 14 acquires, from the reflected wave storage unit 5, the acoustic data of the time when the natural noise is stored, which is stored after the acoustic data of the time when the reverberation is dominant, and acquired. Artificial noise is extracted from. The artificial noise extraction unit 14 outputs the extracted artificial noise to the artificial noise removal unit 6.

  FIG. 11 is a block diagram showing the configuration of the artificial noise extraction unit 14 of FIG. As shown in FIG. 11, the artificial noise extraction unit 14 acquires, from the reflected wave storage unit 5, a replica that acquires acoustic data of a time during which natural noise dominates stored after acoustic data of a time during which reverberation is dominant. It differs from the artificial noise extraction unit 4 of the first embodiment in that it includes the acoustic data acquisition unit 44 for use. The replica acoustic data acquisition unit 44 acquires, from the reflected wave storage unit 5, acoustic data of a predetermined time δt before transmitting the sound wave next to the time to be subjected to the artificial noise removal, and the artificial noise presence determination circuit 41 Output. The artificial noise presence / absence determination circuit 41, the artificial noise removal data generation circuit 42, and the artificial noise Doppler shift generation circuit 43 are the same as those in the first embodiment.

  The artificial noise removing unit 6 removes artificial noise from acoustic data after sound wave transmission prior to acoustic data for which a replica has been acquired using replica noise data output from the artificial noise extracting unit 14.

  According to this embodiment, the same effect as that of the first embodiment can be obtained. Moreover, compared with the structure of 1st Embodiment, it can be set as a simple structure by the point which is not provided with the switch part 2 and the sound memory part 3 before transmission.

  In the above-described embodiment, the active sonar device can realize functions such as artificial noise extraction processing, artificial noise removal processing, and reception signal processing by executing a program stored in a non-volatile memory (not shown). it can. In this case, the program executed by the active sonar device may be stored in a computer readable recording medium, or may be downloaded from a server via a communication line. The active sonar apparatus has a computer system inside, and the processing procedure is stored in a computer-readable recording medium in a program format, and the computer system reads out and executes the program to extract artificial noise. Processing, artificial noise removal processing, received signal processing, and the like can be realized. The “computer system” includes CPU, memory, hardware such as peripheral devices, and software such as an operating system (OS). Also, the "computer system" includes a homepage providing environment / display environment if the WWW system is used.

  In addition, a program for realizing the artificial noise extraction processing, the artificial noise removal processing, the signal processing, etc. shown in the above-mentioned flowchart is recorded on a computer readable recording medium, and the program is read into a computer system and executed. It may be. "Computer readable recording medium" means flexible disk, magneto-optical disk, ROM, writable nonvolatile memory such as flash memory, portable recording medium such as CD-ROM, hard disk incorporated in computer system, etc. Means a storage device.

  The "computer-readable recording medium" is a volatile memory (for example, DRAM) in a computer system serving as a server or client used when transmitting a program via a network such as the Internet, a communication line, or a telephone line. So that the program is held for a certain period of time. You may make it transmit the above-mentioned program to another computer system via the transmission medium from the computer system which stored the memory | storage device, or by the transmission wave in a transmission medium. The “transmission medium for transmitting a program” means a medium having a function of transmitting information, such as a network (communication network) such as the Internet, a telephone line, and a communication line. Moreover, the above-mentioned program may implement | achieve some functions, such as artificial noise extraction which concerns on this invention, artificial noise removal, and signal processing. Or the above-mentioned program is good also as a difference program (or difference file) which implement | achieves the function of this invention in combination with the program already recorded on the computer system.

  While the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments. The configurations and details of the present invention can be modified in various ways that can be understood by those skilled in the art within the scope of the present invention.

  For example, although the sound level of the remaining artificial noise may be high, the calculation load is large, or when the Doppler shift is small, such as when the artificial noise source is at rest, artificial noise extraction in various other cases. The unit 4 may have a configuration in which the artificial noise Doppler shift generation circuit 43 is omitted.

Reference Signs List 1 transducer unit 2 switching unit 3 acoustic transmission unit before transmission 4, 14 artificial noise extraction unit 5 reflected wave storage unit 6 artificial noise removal unit 7 reception signal processing unit 41 artificial noise presence determination circuit 42 data generation for artificial noise removal Circuit 43 Artificial noise Doppler shift generation circuit 61 Removal target data extraction circuit 62 Artificial noise removal data selection circuit 63 Removal data level adjustment circuit 64 Artificial noise subtraction processing circuit

Claims (7)

A transmission unit for transmitting sound waves;
A receiving unit that receives sound waves and outputs acoustic data;
An artificial noise extraction unit that generates replica noise data of a predetermined time length from acoustic data of one or more azimuths in which artificial noise exists before sound wave transmission;
An artificial noise removing unit that removes artificial noise from the acoustic data after sound wave transmission using the replica noise data;
I have a,
The artificial noise removing unit divides the sound data after sound wave transmission into sound data of unit time at predetermined time intervals for each direction, and the sound data of the unit time is based on the sound level of the sound data of the unit time. An active sonar apparatus having a removal target data extraction circuit for determining an azimuth and time in which artificial noise is included . The active sonar device according to claim 1 , wherein the artificial noise extraction unit includes an artificial noise Doppler shift generation unit that generates replica noise data by Doppler shift of the artificial noise.   The active noise reduction method according to claim 1 or 2, further comprising an artificial noise removal data selection unit that correlates the acoustic data after the sound wave transmission with the replica noise data and selects one having high correlation as artificial noise removal data. Sonar device. A signal processing unit that performs signal processing of acoustic data, and a display unit that displays a signal processing result of the signal processing unit,
The active sonar device according to any one of claims 1 to 3, wherein the signal processing unit causes the display unit to display a cell of the direction and time determined to contain the artificial noise . A display unit,
A signal processing unit that causes the display unit to display an input screen for prompting input of a parameter for generating a frequency of Doppler shift in the artificial noise Doppler shift generation unit;
Active sonar device according to claim 2 having a. In a signal processing method of an active sonar device having a wave transmitting unit that transmits sound waves and a wave receiving unit that receives sound waves and outputs acoustic data,
Generate replica noise data of a predetermined length of time from acoustic data in one or more directions where artificial noise exists before transmitting sound waves,
The acoustic data after the sound wave transmission is divided into acoustic data of unit time at predetermined time intervals for each azimuth, and the azimuth including the artificial noise based on the acoustic level of the acoustic data of the unit time And artificial noise is removed from the acoustic data after the sound wave transmission using the replica noise data by determining the time
A signal processing method for an active sonar device . To a computer of an active sonar device having a wave transmitting unit that transmits sound waves and a wave receiving unit that receives sound waves and outputs acoustic data,
A process of generating replica noise data having a predetermined length of time from acoustic data of one or more directions in which artificial noise exists before transmitting sound waves;
The acoustic data after the sound wave transmission is divided into acoustic data of unit time at predetermined time intervals for each azimuth, and the azimuth including the artificial noise based on the acoustic level of the acoustic data of the unit time And a process for determining time,
A program for executing a process of removing artificial noise from acoustic data after sound wave transmission using the replica noise data.

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